The present invention is drawn to a coating for surgical devices that facilitates the incorporation of a surgical device into the tissues at a surgical site.
It has become well known in the surgical arts to utilize various organic (autologous and homologous) and synthetic surgical devices at a surgical site to reinforce or augment the tissues being repaired or otherwise modified. These surgical devices include many distinct structures, including but not limited to surgical meshes, plates, screws, sutures, heart valves, bulking compounds, breast implants, and replacement joints. These devices may be fashioned from many different organic and inorganic materials.
While the functions of the aforementioned surgical devices are varied, the immunostimulating coating of the present invention acts in the same manner regardless of the type of surgical device to which it is applied. The need for a coating such as that of the present invention and the method in which it functions is generally described herein below and with more specificity as the present invention applies to a surgical mesh.
Surgical meshes are porous, gauze-like sheet materials which may be woven or spun from a variety of organic and synthetic materials. Common uses of surgical meshes include the repair of herniations and use as a structural member in gynecological surgeries. The materials from which surgical meshes are made must be biocompatible, chemically and physically inert, non-carcinogenic, mechanically strong, and easily fabricated and sterilized. Most synthetic surgical meshes are woven from monofilament or multifilament fibers to form a mesh having pores of varying sizes and geometries. Other synthetic surgical meshes are formed in a node and fibril arrangement in which the mesh is comprised of larger sections or nodes which are interconnected by fibrils of the mesh material. A non-exhaustive list of common surgical meshes is given in Table 1 below.
Organic surgical meshes are typically derived from human or animal sources. Homologous surgical meshes may be derived from the tissues of a donor, from animal tissues, or from cadaveric tissues. Autologous surgical meshes are meshes that are derived from a patient""s own body, and may comprise dermagraphs, fascia tissues, and dura mater.
The most common use of surgical meshes involves the reinforcement of herniations. Surgical meshes are also used in gynecological procedures including abdominal sacrocolopopexy and as suburethral slings. Other procedures which require surgical meshes include laparosopic retropubic urethropexy, intraperitoneal placement for adhesion prevention, the repair of pelvic floor hernias, rectoceles, and cystoceles. It is to be understood that the aforementioned surgical procedures do not comprise a complete list of all uses of organic and synthetic surgical meshes. New and varied uses for surgical meshes, and for all surgical devices, are being discovered on an ongoing basis and the present invention is to be construed to be applicable to all present and future uses of surgical devices such as a surgical mesh.
In many surgical procedures, it is desirable that a surgical mesh become incorporated into the tissues surrounding a surgical site. One example of such a surgical procedure is the reinforcement and repair of a herniation. In the repair of a hernia, and after the hernia has itself been closed using standard surgical techniques, a surgical mesh of appropriate size and shape is placed over the newly repaired hernia and secured in place using sutures, staples, surgical adhesives, or any other suitable connecting means. As the tissues surrounding the surgical site heal, granulation tissues growing at and around the surgical site begin to produce an extracellular matrix which, in a process called fibrosis, infiltrates and attaches to the material of the surgical mesh secured over the surgical site. Incorporation of the surgical mesh into the surgical site by the extracellular matrix strengthens the tissues at the surgical site and helps prevent re-injury.
The rate of recovery of a patient who has undergone a surgery utilizing a surgical mesh is strongly related to the rate at which the surgical mesh is incorporated into the tissues surrounding the surgical site. The rate of incorporation of the surgical mesh as well as the potential for infection and the potential for clinical complications is in turn related to the physical properties of the surgical mesh used. For example, synthetic meshes having pores or interstices of less than 10 xcexcm in size may theoretically promote infection in that small bacteria (less than 1 xcexcm in size) may enter the surgical site through the mesh, while important and larger macrophages and polymorphonuclear leukocytes are prevented from passing through the mesh to the surgical site. In addition, the number, size, and shape of the pores play an important role in tissue bonding to the surgical mesh. Generally, surgical meshes having larger pore sizes are difficult for fibroblasts to adhere to. Furthermore, if a surgical mesh is too stiff, it may cause continuing mechanical injury to the tissues surrounding the surgical site with which it comes into contact. In these cases, a prolonged inflammatory reaction may significantly increase patient recovery time and may also cause clinical complications such as mesh extrusion and enteric fistulas.
Because the ailments which require the use of surgical meshes are typically quite serious, recovery from surgeries undertaken to alleviate or cure these ailments can be protracted. Therefore, it is desirable to facilitate or speed up the healing and recovery process where surgical meshes are used.
Accordingly, it is an object of the present invention to provide a coating for a surgical device such as a surgical mesh that promotes the rapid incorporation and acceptance of the surgical device by the tissues surrounding the surgical site at which the surgical device has been implanted. Another object of the present invention is to stimulate the immune system to prevent surgical site infections. Yet another object of the present invention is permit the use of synthetic surgical meshes and other surgical devices that are prone to rejection by or more difficult to incorporate into the tissue surrounding a surgical site.
The present invention essentially comprises a xcex2-D-glucan composition that is applied to a preselected surgical device. Preferably, the xcex2-D-glucan composition is a cereal derived xcex2-D-glucan made from one of oats, barley, or wheat, however other sources of xcex2-D-glucan are also contemplated. Examples of other suitable sources of xcex2-D-glucan include microbial sources such as yeast, bacteria, and fungus. A preferred embodiment of the present invention comprises a biocompatible surgical mesh that is typically used for reinforcing a surgical site. These surgical meshes may be synthetic or organic in origin. Synthetic surgical meshes are commonly made from polypropylene, polytetrafluoroethylene, expanded polytetrafluoroethylene, polyethylene terephthalate, polyglycolic acid, polyglactin, dacron-polythene reinforced silicone and polyethylene among others. Organic surgical meshes may be derived from human sources, animal sources, and cadaveric sources.
The present invention also comprises a method of promoting the acceptance of a surgical device into the tissues into which the surgical device is implanted. This method comprises the step of applying an immunostimulating agent comprising a xcex2-D-glucan to the surgical device before implantation thereof at the surgical site.
One method of applying an imunostimulating agent such as xcex2-D-glucan to a biocompatible surgical device comprises the steps of preparing an aqueous solution of a cereal derived xcex2-D-glucan, immersing the pre-selected surgical device in the aqueous solution of xcex2-D-glucan, and evaporating the water component of the aqueous solution. Alternatively, one may prepare sheets of xcex2-D-glucan and apply these preformed sheets of xcex2-D-glucan to a pre-selected surgical device. The sheets are formed by preparing an aqueous solution comprising a cereal derived xcex2-D-glucan and placing the aqueous solution in a drying tray to evaporate the water component of the solution. The residue left in the drying tray is in the form of a xcex2-D-glucan sheet. Sheets of xcex2-D-glucan so formed are then applied to the surgical device by means of a suitable adhesive or by wetting the surgical mesh to partially dissolve the sheet of xcex2-D-glucan.
Another method of applying a xcex2-D-glucan to a surgical device comprises the steps of applying a suitable solvent to the surgical device and then applying a xcex2-D-glucan powder to the wetted surface of the surgical device such that the xcex2-D-glucan powder dissolves into the solvent to form a substantially uniform coating upon the biocompatible surgical device. Finally, the solvent is evaporated from the substantially uniform coating of xcex2-D-glucan upon the biocompatible surgical device.
Another method of applying a immunostimulating coating to a surgical device involves spraying an aqueous solution of the immunostimulating coating onto the surgical device and then evaporating the water component of the solution to leave a suitable coating on the surface of the surgical device. The spraying method may also be used in an electrostatic spraying application that involves giving the aqueous solution being sprayed and the surgical device opposing electrostatic charges such that the aqueous solution is attracted to, and uniformly covers, the surgical device.
Vacuum deposition may also be used to apply an immunostimulating coating to a surgical device. In this application method, an aqueous solution is applied to a selected surgical device and a vacuum is subsequently drawn there around. The vacuum acts to drawn the aqueous solution tightly to the surface of the surgical device. The water component of the aqueous solution is thereafter evaporated to set the coating upon the surgical device.
The objectives and advantages of the invention will be more fully developed in the following description, made in conjunction with the accompanying drawings and wherein like reference characters refer to the same or similar parts throughout the several views.